This application claims priority under 35 USC 119 of Japanese Patent Application No. 2000-101284 filed on Mar. 31, 2000, the entire disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention generally relates to a vehicle transmission that is shifted by an actuator, and more particularly to a transmission that realizes smooth and comfortable starting of a vehicle.
2. Description of the Related Art
A total weight and load of large trucks such as tractor-trailer greatly differs from when the tractor does not tow a trailer (or the trailer is empty and carries no load) to when the tractor tows a fully-loaded trailer. In order to maintain a satisfactory engine running condition and allow a driver to drive a vehicle comfortably in any situations, a large truck has a considerably greater number of gear positions than a small truck (e.g., pick-up truck). For example, the large truck is equipped with a four-gear main gear assembly, a two-gear splitter gear assembly of relatively small gear ratio in front of the main gear assembly, and a two-gear range gear assembly of relatively large gear ratio behind the main gear assembly. The combination of the splitter gear assembly, main gear assembly and range gear assembly provides sixteen gear positions as a whole. By employing such large-number-gear transmission, a driver can select a suitable gear so that an appropriate engine condition is obtained across a wide range of vehicle speed. Further, the driver can accelerate and decelerate the vehicle smoothly.
Gear position change is effected by an actuator under the control of an associated controller. However, initiation of the gear position change is effected by either automatically under the control of the controller or manually. The driver can momentarily tilt a shift lever to the front and back from a D position or range (=H position), which is a stable driving gear position. In the manual shift mode, if the driver moves the shift lever forward from the H position, the controller recognizes that the driver wants to shift up the transmission, and if the driver moves the shift lever backward, the controller assumes that the driver intends to shift down the transmission. Subsequently, the controller shifts up or down the transmission from a current gear position. By repeating this shift up (or down) operation, the transmission gear position is gradually raised (or lowered). If the driver keeps the shift lever in the H position, the current gear position is maintained. In the automatic shift mode, the driver does not have to move the shift lever; instead, even if the shift lever remains in the D position, the controller selects a most appropriate gear position based on an engine running condition and/or vehicle speed and automatically effects the shifting up or down.
Although the transmission has sixteen gears, all the gears from the first to sixteenth are not used during driving. Some of the gears may be frequently utilized depending upon. vehicle load condition, driver""s intention, etc. For instance, when a large truck with a trailer starts moving, a very low gear position such as first or second gear is generally selected if the trailer carries a relatively heavy load. On the other hand, if the load is not so heavy, a relatively high gear position such as fourth, fifth or sixth gear may be selected. In the latter case, the tractor-trailer can smoothly start and accelerate with the relatively high gear, and the driver can experience comfortable starting. Further, since clutch disengagement and engagement take place less frequently as compared with the former case, clutch wear is reduced and its life is elongated. If the tractor does not tow the trailer, a still higher gear such as ninth gear may be selected to experience comfortable starting. The first or second gear may be selected in a particular situation, e.g., when the vehicle starts on an uphill, when an engine torque should be raised because of low atmospheric pressure in mountains, or when the driver should operate the vehicle delicately at a low speed to park in a garage.
In order to start the large truck having sixteen gear positions smoothly, a gear for starting should be selected appropriately based on a vehicle load, road condition, driver""s intention, atmospheric condition, etc. However, the shift lever only allows shifting up and down so that the first gear is always selected in every initial setting and the shift lever operation must be repeated until a desired start gear is reached. Thus, the driver is required to tilt the shift lever repeatedly every time the driver wants to start the vehicle from a stop condition. This is troublesome and a certain period is needed until the vehicle starts, thereby degrading driving comfort.
To solve the above described problem, Japanese Patent Application, Laid Open Publication No. 7-208590 published on Aug. 11, 1995 and entitled xe2x80x9cGear Position Selection Circuit For Use In Semi-Automatic Transmissionxe2x80x9d discloses an arrangement for a tractor-trailer that has a relay connected in series to a key switch and is activated by a trailer pick-up switch which is pneumatically activated by a brake system of the trailer. The relaying operation of the relay determines whether the trailer is towed or not. If a tractor tows the trailer, the transmission is shifted from the first gear to a desired gear successively (gear by gear). If no trailer is pulled, the initial shift up operation made by a driver selects a certain gear higher the first gear, and then the transmission is shifted from that gear successively. It should be remembered here that when the tractor pulls the trailer with a relatively light load, the driver generally wants to start the vehicle at the fourth, fifth or sixth gear. According to the above-mentioned Japanese Patent Publication No. 7-208590, however, the first gear is always selected at the beginning as far as the vehicle pulls the trailer. Further, even if the vehicle does not pull the trailer, the driver has to conduct the first shift up operation to skip. over to a certain gear before reaching a desired gear. Moreover, at least four signal lines are required for the relay in order to determine whether the vehicle tows the trailer or not. It should be noted that there is crowded wiring near the key switch in any vehicle, so that additional wiring. (at least four additional lines) makes the arrangement complicated.
One of the objects of the present invention is to provide an arrangement for a multi-gear transmission that can solve the above problems.
According to one aspect of the present invention, there is provided an apparatus for use with a transmission equipped with an actuator for shifting the transmission and a first contoller for issuing a command to the actuator to control a shifting operation of the transmission, the apparatus including a second controller for selecting one start gear, higher a lowest gear of the transmission, from a plurality of predetermined start gears when starting a vehicle. With this apparatus, if a driver moves a shift lever to a D position, a start gear is automatically selected.
The second controller may select one start gear from two, based on whether the vehicle tows another vehicle or not. The apparatus may further include a sensor for detecting the trailing vehicle, and the second controller may select a single start gear from the two candidates based on detection result from the sensor. The sensor may determine whether there is a trailing vehicle or not based on change in voltage or current of a signal issued to the trailing vehicle from the leading vehicle to illuminate a brake lamp of the trailing vehicle. The sensor may be a contact type or optical type switch mounted on the leading vehicle, and the trailing vehicle is mechanically coupled with the leading vehicle such that a certain portion of the trailing vehicle touches the switch when the trailing vehicle is towed by the leading vehicle. A driver may be able to decide the predetermined start gears.
Additional objects, aspects and advantages of the present invention will become apparent to those skilled in the art to which the invention relates from the subsequent detailed description of the invention and appended claims taken in conjunction with the accompanying drawings.